xtask: Prepare gen_code to have two output files

* Rename `gen_code_as_string` to `gen_uefi_code_as_string`
* Factor out part of that function to a new `code_to_string` function

Author: nicholasbishop

xtask/src/device_path/mod.rs

@@ -7,14 +7,40 @@ use crate::opt::GenCodeOpt;
 use anyhow::{bail, Result};
 use fs_err as fs;
 use group::NodeGroup;
+use proc_macro2::TokenStream;
 use quote::quote;
 use syn::{File, Item};
 use util::rustfmt_string;
 
 const INPUT_PATH: &str = "xtask/src/device_path/spec.rs";
-const OUTPUT_PATH: &str = "uefi/src/proto/device_path/device_path_gen.rs";
+const UEFI_OUTPUT_PATH: &str = "uefi/src/proto/device_path/device_path_gen.rs";
 
-fn gen_code_as_string(groups: &[NodeGroup]) -> Result<String> {
+fn code_to_string(code: TokenStream) -> Result<String> {
+    // Insert some blank lines to make the output a bit more readable,
+    // otherwise everything is entirely squished together. `rustfmt`
+    // doesn't currently handle inserting blank lines very well, even
+    // with the unstable options.
+    let code = code.to_string().replace('}', "}\n\n");
+
+    let output = format!(
+        "
+// DO NOT EDIT
+//
+// This file was automatically generated with:
+// `cargo xtask gen-code`
+//
+// See `/xtask/src/device_path/README.md` for more details.
+#![allow(clippy::missing_const_for_fn)]
+
+{code}"
+    );
+
+    let formatted = rustfmt_string(output)?;
+
+    Ok(formatted)
+}
+
+fn gen_uefi_code_as_string(groups: &[NodeGroup]) -> Result<String> {
     let packed_modules = groups.iter().map(NodeGroup::gen_packed_module);
     let node_enum = NodeGroup::gen_node_enum(groups);
     let build_modules = groups.iter().map(NodeGroup::gen_builder_module);
@@ -52,28 +78,7 @@ fn gen_code_as_string(groups: &[NodeGroup]) -> Result<String> {
         }
     );
 
-    // Insert some blank lines to make the output a bit more readable,
-    // otherwise everything is entirely squished together. `rustfmt`
-    // doesn't currently handle inserting blank lines very well, even
-    // with the unstable options.
-    let code = code.to_string().replace('}', "}\n\n");
-
-    let output = format!(
-        "
-// DO NOT EDIT
-//
-// This file was automatically generated with:
-// `cargo xtask gen-code`
-//
-// See `/xtask/src/device_path/README.md` for more details.
-#![allow(clippy::missing_const_for_fn)]
-
-{code}"
-    );
-
-    let formatted = rustfmt_string(output)?;
-
-    Ok(formatted)
+    code_to_string(code)
 }
 
 fn parse_spec(spec_str: &str) -> Vec<NodeGroup> {
@@ -95,14 +100,14 @@ pub fn gen_code(opt: &GenCodeOpt) -> Result<()> {
     let spec_str = include_str!("spec.rs");
 
     let groups = parse_spec(spec_str);
-    let output_string = gen_code_as_string(&groups)?;
+    let uefi_output_string = gen_uefi_code_as_string(&groups)?;
 
     if opt.check {
         // Implementation note: we don't use `rustfmt --check` because
         // it always exits zero when reading from stdin:
         // https://github.com/rust-lang/rustfmt/issues/5376
 
-        if output_string != fs::read_to_string(OUTPUT_PATH)? {
+        if uefi_output_string != fs::read_to_string(UEFI_OUTPUT_PATH)? {
             bail!("generated code is stale");
         }
 
@@ -111,7 +116,7 @@ pub fn gen_code(opt: &GenCodeOpt) -> Result<()> {
             bail!("spec.rs needs formatting");
         }
     } else {
-        fs::write(OUTPUT_PATH, output_string)?;
+        fs::write(UEFI_OUTPUT_PATH, uefi_output_string)?;
 
         // Also format the input file. It's valid rust, but not included
         // via `mod` anywhere, so the usual `cargo fmt --all` doesn't